Hyla japonica is a member of the Hyla arborea complex. A number of authors consider H. japonica to be a subspecies of H. arborea, but biochemical and morphological differences between these two forms confirm the specific rank of H. japonica. Fei (1999) considered H. ussuriensis from northern China, the Korean Peninsula, eastern Russia and Mongolia to be a separate species from H. japonica on Japan. Here we consider H. ussuriensis to be a synonym of H. japonica pending further taxonomic work on this complex.

Justification:
Listed as Least Concern in view of its wide distribution, tolerance of a broad range of habitats, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

This species is widespread in Japan (Hokkaido, Honshu, Shikoku, Kyushu and other small islands), central, northern and northeastern China, it is found throughout both the Democratic People's Republic of Korea and the Republic of Korea, present in northern Mongolia and the southern Russian Far East.

This species inhabits mixed and deciduous broadleaved forests, forest steppes, bush lands, meadows, swamps, paddy fields, ponds, and the surrounding vegetation. It is often found along the banks of rivers, streams, and lakes. Spawning and larval development takes place in stagnant ponds, puddles, oxbow lakes, flooded quarries, and lakes with dense herbaceous vegetation. The eggs are sometimes deposited in river and stream pools. The species tolerates some degree of habitat modification, and may even be found in large cities.

The threats to this species are not well known, but are presumed to include general habitat loss, (often from changes in land use such as conversion of paddy fields to vegetable farming), pollution and prolonged drought in arid areas.